Author Topic: ever heard of this? (Read 531 times)

thelaw · « **on:** July 19, 2005, 10:33:09 AM »

first of all after 40rounds of the WWB 45gr. hp, i've determined its not for my handi. the best group i've gotten is about 1.25" with the WWB. handloaded 50gr. v-max definitely shoot better for me. usually always under 1".

on to my question, today i was out trying a load with the 50gr. v-max. i shot a 5 shot group that interestingly enough shot about .75"@ 100yds, however with all 5 shots the velocity increased a good bit. the first shot was 3115fps and shot #5 was all the way up to 3421fps. what would cause this other than a powder charging mishap?

870 expressmag · « **Reply #1 on:** July 19, 2005, 10:37:04 AM »

i guess i am just going off what would maybe be logical in my head(which is scary)....would you maybe have fouling or powder buildup each time which would cause more constriction and higher pressures therefore transforming into higher fps??

Longcruise · « **Reply #2 on:** July 19, 2005, 01:27:54 PM »

Could be erratuc lighting on the chrono or a poor battery in the chrono. Could be factual info too :shock:

A load with such a broad spread can shoot at 100 yards but you might test it at 300 or 400 to see if it begins to string vertically due to velocity differential.

I'd reshoot with a new battery and a cloudy day and maybe measure ten shots to get a better picture. BTW, was your ammo sitting in the sun while you fired the string?

thelaw · « **Reply #3 on:** July 19, 2005, 01:31:21 PM »

there was significant blackening around the outside of the case necks as the velocity got up there. how could i have had fouling or powder build up though, i had just cleaned the rifle chamber and barrel and had not put but about 10 round thru it when this started? never happened before. my load was 26.5gr. of H335 with a 50gr. vmax. before it i had shot a load of 26.0 of H335 with no pressure signs at all.

thelaw · « **Reply #4 on:** July 19, 2005, 01:58:25 PM »

i had just put a new battery in it.

Brett · « **Reply #5 on:** July 19, 2005, 04:35:13 PM »

How did you measure your powder when you were loading? Did you use a dipper or did you use a trickler and weigh each charge on a scale? Could the calibration of the scale have changed from charge to charge somehow? The shells sitting in the direct sun theory has merrit also I believe.

thelaw · « **Reply #6 on:** July 20, 2005, 06:37:51 AM »

the shells were in a shell box in under a top and each shell was trickled individually and measured on digital scales, which i zero ever couple of rounds.

rbjaw · « **Reply #7 on:** July 20, 2005, 09:09:55 AM »

the law
the bullets were not moly coated.....
barrel allowed to cool between shots eh!
cooking round in chamber for barrel to cool?

jaw